In video system applications, random noise present in analog video signals, such as NTSC or PAL signals, for example, may result in images that are less than visually pleasing to the viewer. To address this problem, noise reduction (NR) operations may be utilized to remove or mitigate the analog noise present. However, some NR operations may result in visual artifacts such as motion trails, jittering, and/or wobbling that may result from excessive filtering. To reduce these effects, consideration may be given to whether the analog video noise is present in a static area or in an area where there is significant motion in the video content.
Some traditional NR operations may be performed independent of the analog noise level. For example, filter coefficients may be set conservatively to avoid over filtering for relatively clean videos. However, conservative filtering may result in many instances where noise remains in the video signal and affects the perceptual quality. Analog noise levels may be determined when conducting other traditional NR operations, however, the analog noise level may be determined by some external methods that do not explicitly operate on the video content. For example, the analog noise level may be estimated by measuring the variance in the blanking levels of the NSTC/PAL signal, usually by a module that is utilized to decode the NTSC/PAL signal. This approach makes the NR operation more tightly coupled with the NTSC/PAL decoding and not a separate or independent operation.
In order to improve NR operations it may be necessary to characterize the noise present in the video signal and select filter coefficients accordingly. However, noise characterization may be difficult to achieve since there may be many different noise sources. While white noise may be generally characterized as a Gaussian distribution in both the spatial and temporal domain, other types of analog noises in the video signals may not be easily estimated.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.